MR23B-2658
Crystal Structure and Equations of State of Synthetic Chondrodite and Clinohumite: Implications for Water in the Upper Mantle
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Yu Ye, China University of Geosciences Wuhan, Wuhan, China
Abstract:
Chondrodite and clinohumite were observed as dehydration products of serpentine and in experiments of pure MgO-SiO2-H2O systems at pressures of 5~12 GPa . They could serve as H2O carriers in the upper mantle and transition zone in hydrous compositional systems. Due to the critical role of water in controlling silicate phase relations and physical properties of the upper mantle, the crystal structures and physical properties of DHMS have been extensively studied. We synthesized coexisting phases of OH-clinohumite and hydrous olivine in multi-anvil press (P = 12 GPa, T = 1523 K), at Bayerisches Geoinstitut, Germany. OH-chondrodite and OH-clinohumite were characterized by Raman, and their crystal structures were refined by single-crystal X-ray diffraction (XRD). We also studied their thermal expansivities by single-crystal (XRD), and the elasticity of by Brillouin Spectroscopy. We further constrain on Systematic trends between H2O content and physical properties among dense hydrous magnesium silicate (DHMS) phases along the forsterite-brucite join, such as thermal expansivity, compressibility, elasticity, as well as grüneisen parameters. This study suggests that hydrogen has significant effect on the physical properties of the upper mantle, and understanding the physical and chemical behaviors of DHMS phases is important for the study of water cycling in the mantle.